CN115128144A

CN115128144A - Gas sensor

Info

Publication number: CN115128144A
Application number: CN202210122969.0A
Authority: CN
Inventors: 安立光辉; 片桐康太
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 2021-03-24
Filing date: 2022-02-09
Publication date: 2022-09-30
Also published as: JP2022147914A; DE102022000477A1; US20220308009A1

Abstract

The invention provides a gas sensor which can realize a stable chiseled shape even if a chiseled part of a housing is pressed from above in a manufacturing process. The gas sensor includes a sensor element, a holding member, and a housing. The sensor element is used for measuring the concentration of a predetermined gas component in a gas to be measured. The holding member holds a part of the sensor element. The housing accommodates the sensor element and the holding member. The housing includes a cylindrical base portion and a cylindrical caulking portion. The caulking portion is provided further toward the rear end side than the base portion, and presses the position on the rear end side of the holding member in a bent state. The chiseling portion has a cutout portion formed in a part in the circumferential direction.

Description

Gas sensor

Technical Field

The present invention relates to a gas sensor.

Background

Japanese patent No. 3885781 (patent document 1) discloses a gas sensor. In the gas sensor, the sensor element is housed in a cylindrical case. In this gas sensor, the cylindrical fixing portion formed at the rear end portion of the housing is bent and deformed, thereby caulking and fixing the housing and the sensor element.

Documents of the prior art

Patent literature

Patent document 1: japanese patent No. 3885781

Disclosure of Invention

In the gas sensor disclosed in patent document 1, the cylindrical fixing portion is pressed from above, and the housing and the sensor element are fixed by caulking. However, in the gas sensor, the cylindrical diameter-reduced portion of the cylindrical fixing portion may have insufficient strength. As a result, a stable caulking shape may not be achieved.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a gas sensor that can realize a stable caulking shape even when a caulking portion of a housing is pressed from above during a manufacturing process.

A gas sensor according to the present invention includes a sensor element, a holding member, and a housing. The sensor element is used for measuring the concentration of a predetermined gas component in a gas to be measured. The holding member holds a part of the sensor element. The housing accommodates the sensor element and the holding member. The housing includes a cylindrical base portion and a cylindrical caulking portion. The caulking portion is provided further toward the rear end side than the base portion, and presses the position on the rear end side of the holding member in a bent state. The chisel portion has a cutout portion formed in a part in the circumferential direction.

Regarding the gouging portion, a case where a cut is not formed in a part in the circumferential direction is considered. In this case, if the gouging portion is gouged, the rear end of the gouging portion is pushed radially inward, and therefore the length of the rear end of the gouging portion in the circumferential direction is shortened. As a result, the remaining portion of the bent portion of the gouging portion is swept radially outward, and lateral bulging of the gouging portion, for example, occurs. In this gas sensor, the cut-out portion is formed in a part of the chiseling portion in the circumferential direction. Therefore, even if the caulking portion is caulked and the rear end of the caulking portion is pushed inward in the radial direction, the bent portion is easily accommodated inside in the radial direction as compared with a case where the notch portion is not formed. As a result, according to this gas sensor, even if the gouge portion is gouged, a part of the gouge portion is hard to be caught to the outside in the radial direction, and thus lateral bulging of the gouge portion is hard to occur.

In the gas sensor, a ratio of a length of the cutout in the outer periphery of the gouge to a length of the entire outer periphery of the gouge may be 0.3 or more.

In the gas sensor, a ratio of a length of the cutout in the outer periphery of the gouge to a length of the entire outer periphery of the gouge may be 0.25 to 0.45.

In the gas sensor, the number of the notches formed in the caulking portion may be 4 to 6.

In the gas sensor, a length from a position corresponding to the rear end of the gouge portion to a bottom of the cutout portion may be 2.00mm or more and 3.00mm or less.

In the gas sensor, the thickness of the caulking portion may be 0.45mm to 0.65 mm.

Effects of the invention

According to the present invention, it is possible to provide a gas sensor that can realize a stable caulking shape even when the caulking portion of the housing is pressed from above during the manufacturing process.

Drawings

Fig. 1 is a schematic diagram showing a longitudinal section of a part of a gas sensor.

Fig. 2 is a schematic cross-sectional view schematically showing an example of the structure of the sensor element.

Fig. 3 is a diagram schematically showing a vertical cross section of the housing before the gouging section is gouged.

Fig. 4 is a diagram schematically showing a state in which a part of the bur is viewed from the side.

Fig. 5 is a view schematically showing a V-V section of fig. 3.

Fig. 6 is a schematic diagram showing a state where the chiseling section is chiseled from the rear.

Fig. 7 is a schematic cross-sectional view schematically showing an example of the structure of the sensor element having a three-cavity structure.

Fig. 8 is a diagram corresponding to fig. 5 of a modification.

Fig. 9 is a schematic explanatory diagram of a leak test using a tester.

Fig. 10 is a diagram showing an example of the calking shape of comparative example 1.

Fig. 11 is a diagram showing an example of the calking shape of embodiment 1.

Description of the reference numerals

1 … first substrate layer, 2 … second substrate layer, 3 … third substrate layer, 4 … first solid electrolyte layer, 5 … separator layer, 6 … second solid electrolyte layer, 10 … gas inlet port, 11 … first diffusion rate control section, 12 … buffer space, 13 … second diffusion rate control section, 20 … first internal cavity, 21 … main pump cell, 22 … internal side pump electrode, 22a, 51aX … top electrode section, 22b, 51bX … bottom electrode section, 23 … external side pump electrode, 30 … third diffusion rate control section, 40X … second internal cavity, 41 … measuring pump cell, 42 … reference electrode, 43 … reference gas inlet space, 44X … measuring electrode, 45 … fourth diffusion rate control section, 46, 52 … variable power supply, 48 … atmospheric air inlet layer, 50 … auxiliary pump cell, 51X … auxiliary pump electrode, 60 … fifth diffusion speed control part, 61 … third internal cavity, 70 … heater part, 71 … heater electrode, 72 … heater, 73 … through hole, 74 … heater insulation layer, 75 … pressure release hole, 80 … main pump control oxygen partial pressure detection sensor unit, 81 … auxiliary pump control oxygen partial pressure detection sensor unit, 82 … measurement pump control oxygen partial pressure detection sensor unit, 83 … sensor unit, 90 … protection layer, 100 … gas sensor, 101 … sensor element, 130 … protection cover, 140Y … housing, 141 … base, 142Y … encrustation part, 143 … holding member, 144a, 144b … ceramic support, 145 … powder, 200 … notch, 500 … tester, 502 … mounting jig, 504 … upper cover, 506 … lower cover, 508 … tube, 510 … film.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and description thereof will not be repeated.

[1. gas sensor Overall Structure ]

Fig. 1 is a diagram schematically showing a longitudinal section of a part of a gas sensor 100 according to the present embodiment. In each drawing, the longitudinal direction of the sensor element 101 described later is the front-rear direction, and the thickness direction of the sensor element 101 is the up-down direction.

As shown in fig. 1, the gas sensor 100 is mounted on a pipe such as an exhaust pipe of a vehicle. The gas sensor 100 is configured to: the concentration of a predetermined gas component in a gas to be measured such as an exhaust gas is measured. Examples of the predetermined gas component include NOx and O ₂ . The gas sensor 100 according to the present embodiment is configured such that: the NOx concentration in the gas to be measured is measured.

The gas sensor 100 includes a sensor element 101, a protective cover 130, a holding member 143, and a housing 140. The sensor element 101 has a long rectangular parallelepiped shape and detects a predetermined gas component in a gas to be measured. Hereinafter, the sensor element 101 is explained in detail. The protective cover 130 is cylindrical and covers the periphery of the distal end of the sensor element 101.

The holding member 143 includes

ceramic supports

144a and 144b and a green compact 145. The ceramic supports 144a and 144b and the green compact 145 cover the periphery of the sensor element 101 in the case 140 and hold the sensor element 101.

The housing 140 is made of metal, and includes a cylindrical base portion 141 and a cylindrical caulking portion 142. The

ceramic bearings

144a and 144b and the green compact 145 are sealed inside the base 141. The inner diameter of the case 140 on the front end side is smaller than the inner diameter on the rear end side. The tip of the ceramic receiver 144a engages with the inner circumferential surface of the portion of the housing 140 having a shorter inner diameter. Accordingly, the holding member 143 does not fall off from the front of the housing 140.

The sensor element 101 is positioned on the central axis of each of the holding member 143 and the housing 140, and penetrates the holding member 143 and the housing 140 in the front-rear direction.

The caulking portion 142 is provided further toward the rear end side than the base portion 141, and presses the position on the rear end side of the holding member 143 (ceramic support 144b) in a bent state. The tapered portion 142 is formed over the entire circumference in the circumferential direction. The gouging process is performed from above (rearward in the drawing) to bend the gouging portion 142. Accordingly, the holding member 143 is fixed in the housing 140. The thickness of the densified portion 142 is thinner than that of the base portion 141. Hereinafter, the encryptor 142 is explained in detail.

[2. Structure of sensor element ]

Fig. 2 is a schematic cross-sectional view schematically showing an example of the structure of the sensor element 101 included in the gas sensor 100. The sensor element 101 is formed of zirconia (ZrO) in this order from the lower side in the drawing ₂ ) An element having a structure in which 6 layers of a first substrate layer 1, a second substrate layer 2, a third substrate layer 3, a first solid electrolyte layer 4, a separator 5, and a second solid electrolyte layer 6, which are composed of plasma-conductive solid electrolyte layers, are laminated. In addition, the solid electrolyte forming these 6 layers is a dense and airtight solid electrolyte. Such a sensor element 101 is manufactured in the following manner: for example, the ceramic green sheets corresponding to the respective layers are subjected to predetermined processing, printing of a circuit pattern, and the like, and then stacked, and further fired to integrate them.

The front end of the sensor element 101 is covered with the protective layer 90. The protective layer 90 is made of a porous material, for example, ceramic containing ceramic particles. Examples of the ceramic particles include: alumina (Al) ₂ O ₃ ) Zirconium oxide (ZrO) ₂ ) Spinel (MgAl) ₂ O ₄ ) Mullite (Al) ₆ O ₁₃ Si ₂ ) Etc., and the protective layer 90 preferably contains at least any one of these ceramic particles. In the present embodiment, the protective layer 90 is made of an alumina porous body.

A gas introduction port 10, a first diffusion rate controller 11, a buffer space 12, a second diffusion rate controller 13, a first internal cavity 20, a third diffusion rate controller 30, and a second internal cavity 40 are formed adjacent to each other in this order between the lower surface of the second solid electrolyte layer 6 and the upper surface of the first solid electrolyte layer 4 at one end of the sensor element 101.

The gas introduction port 10, the buffer space 12, the first internal cavity 20, and the second internal cavity 40 are spaces inside the sensor element 101 provided by hollowing out the separator 5, wherein the upper portions thereof are defined by the lower surface of the second solid electrolyte layer 6, the lower portions thereof are defined by the upper surface of the first solid electrolyte layer 4, and the side portions thereof are defined by the side surfaces of the separator 5.

The first diffusion rate controlling section 11, the second diffusion rate controlling section 13, and the third diffusion rate controlling section 30 are each provided with 2 horizontally long slits (the longitudinal direction of the opening is in the direction perpendicular to the drawing). A region from the gas inlet 10 to the second internal cavity 40 is also referred to as a gas flow portion.

Further, a reference gas introduction space 43 is provided between the upper surface of the third substrate layers 3 and the lower surface of the separator layer 5 at a position farther from the tip side than the gas flow portion, and at a position where the side portion is partitioned by the side surface of the first solid electrolyte layer 4. For example, the atmosphere is introduced into the reference gas introduction space 43. Note that the first solid electrolyte layer 4 may extend to the rear end of the sensor element 101 without forming the reference gas introduction space 43. In addition, in the case where the reference gas introduction space 43 is not formed, the atmosphere introduction layer 48 may extend to the rear end of the sensor element 101 (for example, see fig. 7).

The atmosphere introduction layer 48 is a layer made of porous alumina, and the reference gas is introduced into the atmosphere introduction layer 48 through the reference gas introduction space 43. Further, the atmosphere introduction layer 48 is formed of: the reference electrode 42 is covered.

The reference electrode 42 is an electrode formed so as to be sandwiched between the upper surface of the third substrate layer 3 and the first solid electrolyte layer 4, and as described above, an atmosphere introduction layer 48 communicating with the reference gas introduction space 43 is provided around the reference electrode. As will be described later, the oxygen concentration (oxygen partial pressure) in the first internal cavity 20 and the second internal cavity 40 can be measured by the reference electrode 42.

In the gas flow portion, the gas inlet 10 is a portion opened to the external space, and the gas to be measured enters the sensor element 101 from the external space through the gas inlet 10.

The first diffusion rate controller 11 is a part that applies a predetermined diffusion resistance to the gas to be measured entering from the gas inlet 10.

The buffer space 12 is a space provided to guide the gas to be measured introduced from the first diffusion rate controller 11 to the second diffusion rate controller 13.

The second diffusion rate controller 13 is a portion that applies a predetermined diffusion resistance to the gas to be measured introduced from the buffer space 12 into the first internal cavity 20.

When the gas to be measured is introduced into the first internal cavity 20 from the outside of the sensor element 101, the gas to be measured that has suddenly entered the sensor element 101 from the gas introduction port 10 due to the pressure variation of the gas to be measured in the external space (pulsation of the exhaust pressure in the case where the gas to be measured is the exhaust gas of an automobile) is not directly introduced into the first internal cavity 20, but is introduced into the first internal cavity 20 after the concentration variation of the gas to be measured is eliminated by the first diffusion rate control unit 11, the buffer space 12, and the second diffusion rate control unit 13. Thus, the concentration of the gas to be measured introduced into the first internal space varies to a negligible extent.

The first internal cavity 20 is provided as a space for adjusting the oxygen partial pressure in the gas to be measured introduced by the second diffusion rate control unit 13. Such an oxygen partial pressure is adjusted by operating the main pump unit 21.

The main pump unit 21 is an electrochemical pump unit configured to include: an inner pump electrode 22 having a top electrode portion 22a provided on substantially the entire surface of the lower surface of the second solid electrolyte layer 6 facing the first internal cavity 20; an outer pump electrode 23 provided in a region corresponding to the top electrode portion 22a on the upper surface of the second solid electrolyte layer 6 so as to be exposed to the outside space; and a second solid electrolyte layer 6 sandwiched by the electrodes.

The inner pump electrode 22 is formed so as to straddle the solid electrolyte layers (the second solid electrolyte layer 6 and the first solid electrolyte layer 4) formed above and below the first internal cavity 20 and the spacer 5 constituting the side wall. Specifically, a top electrode portion 22a is formed on the lower surface of the second solid electrolyte layer 6 constituting the top surface of the first internal cavity 20, and a bottom electrode portion 22b is formed on the upper surface of the first solid electrolyte layer 4 constituting the bottom surface. Side electrode portions (not shown) are formed on side wall surfaces (inner surfaces) of the spacers 5 constituting the two side wall portions of the first internal cavity 20 so as to be connected to the top electrode portion 22a and the bottom electrode portion 22 b. That is, the inner pump electrode 22 is arranged in a tunnel-like structure at the position where the side electrode portion is arranged.

The inner pump electrode 22 and the outer pump electrode 23 are formed as porous cermet electrodes (e.g., Pt and ZrO containing 1% Au) ₂ The cermet electrode of (a). The inner pump electrode 22 that is in contact with the gas to be measured is formed using a material that can reduce the reducing ability for the NOx component in the gas to be measured.

In the main pump unit 21, by applying a desired pump voltage Vp0 between the inner pump electrode 22 and the outer pump electrode 23 and causing a pump current Ip0 to flow between the inner pump electrode 22 and the outer pump electrode 23 in the positive or negative direction, oxygen in the first internal cavity 20 can be sucked into the external space or oxygen in the external space can be sucked into the first internal cavity 20.

In order to detect the oxygen concentration (oxygen partial pressure) in the atmosphere of the first internal cavity 20, the main pump control oxygen partial pressure detection sensor cell 80 (i.e., electrochemical sensor cell) is configured to include the inner pump electrode 22, the second solid electrolyte layer 6, the separator 5, the first solid electrolyte layer 4, the third substrate layer 3, and the reference electrode 42.

The oxygen concentration (oxygen partial pressure) in the first internal cavity 20 can be determined by measuring the electromotive force V0 of the main pump control oxygen partial pressure detection sensor unit 80. Further, feedback control is performed on Vp0 so that the electromotive force V0 is constant, whereby the pump current Ip0 is controlled. Accordingly, the oxygen concentration in the first internal cavity 20 can be maintained at a predetermined constant value.

The third diffusion rate control portion 30 is a portion that applies a predetermined diffusion resistance to the gas to be measured whose oxygen concentration (oxygen partial pressure) is controlled by the operation of the main pump unit 21 in the first internal cavity 20, and guides the gas to be measured to the second internal cavity 40.

The second internal cavity 40 is provided as a space for performing processing related to measurement of the concentration of nitrogen oxide (NOx) in the gas to be measured introduced by the third diffusion rate control portion 30. In the second internal cavity 40 in which the oxygen concentration is mainly adjusted by the auxiliary pump unit 50, the NOx concentration is measured by the operation of the measurement pump unit 41.

In the second internal cavity 40, the oxygen partial pressure of the gas to be measured introduced through the third diffusion rate control unit after the oxygen concentration (oxygen partial pressure) has been adjusted in the first internal cavity 20 in advance is further adjusted by the auxiliary pump unit 50. Accordingly, the oxygen concentration in the second internal cavity 40 can be kept constant with high accuracy, and therefore, the NOx concentration can be measured with high accuracy in such a gas sensor 100.

The auxiliary pump unit 50 is an auxiliary electrochemical pump unit configured to include: an auxiliary pump electrode 51 having a top electrode portion 51a, the top electrode portion 51a being provided on substantially the entire area of the lower surface of the second solid electrolyte layer 6 facing the second internal cavity 40; an outer pump electrode 23 (not limited to the outer pump electrode 23, as long as it is an appropriate electrode outside the sensor element 101); and a second solid electrolyte layer 6.

The auxiliary pump electrode 51 is disposed in the second internal cavity 40 in the same tunnel-like structure as the inner pump electrode 22 provided in the first internal cavity 20. That is, the top electrode portion 51a is formed on the second solid electrolyte layer 6 constituting the top surface of the second internal cavity 40, and the bottom electrode portion 51b is formed on the first solid electrolyte layer 4 constituting the bottom surface of the second internal cavity 40. Side electrode portions (not shown) connecting the top electrode portion 51a and the bottom electrode portion 51b are formed on both wall surfaces of the spacer 5 constituting the side wall of the second internal cavity 40. That is, the auxiliary pump electrode 51 is disposed in a tunnel-like structure at the portion where the side electrode portion is disposed.

The auxiliary pump electrode 51 is also formed using a material that can reduce the reducing ability for the NOx component in the measurement gas, similarly to the inner pump electrode 22.

In the auxiliary pump unit 50, by applying a desired voltage Vp1 between the auxiliary pump electrode 51 and the outer pump electrode 23, oxygen in the atmosphere in the second internal cavity 40 can be sucked into the external space or oxygen can be sucked into the second internal cavity 40 from the external space.

In order to control the oxygen partial pressure in the atmosphere in the second internal cavity 40, the electrochemical sensor cell, that is, the auxiliary pump control oxygen partial pressure detection sensor cell 81 is configured to include the auxiliary pump electrode 51, the reference electrode 42, the second solid electrolyte layer 6, the separator 5, the first solid electrolyte layer 4, and the third substrate layer 3.

The auxiliary pump unit 50 pumps the fluid by the variable power supply 52 whose voltage is controlled based on the electromotive force V1 detected by the auxiliary pump control oxygen partial pressure detection sensor unit 81. Accordingly, the oxygen partial pressure in the atmosphere within the second internal cavity 40 is controlled to a lower partial pressure that has substantially no effect on the determination of NOx.

At the same time, the pump current Ip1 is used to control the electromotive force of the oxygen partial pressure detection sensor cell 80 for main pump control. Specifically, the pump current Ip1 is input as a control signal to the main pump control oxygen partial pressure detection sensor unit 80, and the gradient of the oxygen partial pressure in the gas to be measured introduced from the third diffusion rate control portion 30 into the second internal cavity 40 is controlled to be constant by controlling the electromotive force V0. When used as a NOx sensor, the oxygen concentration in the second internal cavity 40 is maintained at a constant value of about 0.001ppm by the action of the main pump unit 21 and the auxiliary pump unit 50.

The measurement pump unit 41 measures the NOx concentration in the measurement gas in the second internal cavity 40. The measurement pump cell 41 is an electrochemical pump cell configured to include: a measurement electrode 44 provided on the upper surface of the first solid electrolyte layer 4 at a position facing the second internal cavity 40 and away from the third diffusion rate controlling section 30; an outer pump electrode 23; a second solid electrolyte layer 6; an isolation layer 5; and a first solid electrolyte layer 4.

The measurement electrode 44 is a porous cermet electrode. The measurement electrode 44 also functions as an NOx reduction catalyst that reduces NOx present in the atmosphere in the second internal cavity 40. The measurement electrode 44 is covered with a fourth diffusion rate controller 45.

The fourth diffusion rate controlling section 45 is made of alumina (Al) ₂ O ₃ ) A film comprising a porous body as a main component. The fourth diffusion rate control unit 45 plays a role of limiting the amount of NOx flowing into the measurement electrode 44, and also functions as a protective film for the measurement electrode 44.

In the measurement pump unit 41, oxygen generated by decomposition of nitrogen oxides in the atmosphere around the measurement electrode 44 can be sucked out, and the amount of generated oxygen can be detected as the pump current Ip 2.

In order to detect the oxygen partial pressure around the measurement electrode 44, the electrochemical sensor cell, i.e., the pump control oxygen partial pressure detection sensor cell 82 for measurement is configured to include the second solid electrolyte layer 6, the separation layer 5, the first solid electrolyte layer 4, the third substrate layer 3, the measurement electrode 44, and the reference electrode 42. The variable power supply 46 is controlled based on the electromotive force (control voltage) V2 detected by the measurement pump control oxygen partial pressure detection sensor unit 82.

The gas to be measured guided into the second internal cavity 40 passes through the fourth diffusion rate controlling section 45 under the condition that the oxygen partial pressure is controlled, and reaches the measurement electrode 44. Nitrogen oxide in the measurement gas around the measurement electrode 44 is reduced (2NO → N) ₂ +O ₂ ) Thereby generating oxygen. Then, the generated oxygen is measured and pumped by the pump unit 41, and at this time, the voltage Vp2 of the variable power supply is controlled to: the electromotive force (control voltage) V2 detected by the measurement pump control oxygen partial pressure detection sensor unit 82 is made constant. The amount of oxygen generated around the measuring electrode 44 is equal toSince the concentration of nitrogen oxide in the measurement target gas is proportional, the concentration of nitrogen oxide in the measurement target gas is calculated by the pump current Ip2 in the measurement pump unit 41.

Further, if the measurement electrode 44, the first solid electrolyte layer 4, the third substrate layer 3, and the reference electrode 42 are combined to constitute the oxygen partial pressure detection means in the form of an electrochemical sensor cell, it is possible to detect an electromotive force corresponding to a difference between the amount of oxygen generated by reduction of the NOx component in the atmosphere around the measurement electrode 44 and the amount of oxygen contained in the reference atmosphere, and thereby it is also possible to obtain the concentration of the NOx component in the measurement gas.

The electrochemical sensor cell 83 is configured to include the second solid electrolyte layer 6, the separator 5, the first solid electrolyte layer 4, the third substrate layer 3, the outer pump electrode 23, and the reference electrode 42, and is capable of detecting the oxygen partial pressure in the measurement target gas outside the sensor by using the electromotive force Vref obtained by the sensor cell 83.

In the gas sensor 100 having such a configuration, the main pump means 21 and the auxiliary pump means 50 are operated to supply the measurement target gas, whose oxygen partial pressure is constantly kept at a constant low value (a value that does not substantially affect the measurement of NOx), to the measurement pump means 41. Therefore, the NOx concentration in the measurement target gas can be known based on the pump current Ip2 which is substantially proportional to the NOx concentration in the measurement target gas and flows by sucking out oxygen generated by reduction of NOx from the measurement pump cell 41.

The sensor element 101 further includes a heater unit 70, and the heater unit 70 performs a temperature adjustment function of heating and holding the sensor element 101 so as to improve oxygen ion conductivity of the solid electrolyte. The heater section 70 includes a heater electrode 71, a heater 72, a through hole 73, a heater insulating layer 74, and a pressure release hole 75.

The heater electrode 71 is an electrode formed so as to be in contact with the lower surface of the first substrate layer 1. The heater electrode 71 is connected to an external power supply, whereby power can be supplied from the outside to the heater portion 70.

The heater 72 is a resistor body formed so as to be sandwiched between the second substrate layer 2 and the third substrate layer 3 from the upper and lower sides. The heater 72 is connected to the heater electrode 71 through the through hole 73, and generates heat by being supplied with power from the outside through the heater electrode 71, thereby heating and insulating the solid electrolyte forming the sensor element 101.

The heater 72 is embedded in the entire region from the first internal cavity 20 to the second internal cavity 40, and the temperature of the entire sensor element 101 can be adjusted to activate the solid electrolyte.

The heater insulating layer 74 is an insulating layer formed of an insulator such as alumina on the upper and lower surfaces of the heater 72. The heater insulating layer 74 is formed for the purpose of obtaining electrical insulation between the second substrate layer 2 and the heater 72 and electrical insulation between the third substrate layer 3 and the heater 72.

The pressure release hole 75 is a portion provided to penetrate the third substrate layer 3 and communicate with the reference gas introduction space 43, and is formed for the purpose of alleviating an increase in internal pressure due to a temperature increase in the heater insulating layer 74.

[3. Structure of housing ]

Fig. 3 is a diagram schematically showing a vertical cross section of the housing 140 before the caulking section 142 is caulked. Fig. 4 is a diagram schematically showing a state in which a part of the bur 142 is viewed from the side. Fig. 5 is a view schematically showing the V-V section of fig. 3.

Referring to fig. 3, 4, and 5, the chiseling portion 142 extends further toward the rear end side from the rear end portion of the base portion 141. The thickness of the densified portion 142 is smaller than that of the base portion 141, and is, for example, 0.45mm to 0.65mm, and is, for example, about 0.56 mm.

The chiseling portion 142 is formed with notches 200 at predetermined intervals in the circumferential direction. Each of the cutouts 200 is formed by partially grooving the annular rear end to the front side in the caulking portion 142. The depth D1 (fig. 4) of each notch 200 is, for example, 2.00mm to 3.00mm, and is, for example, about 2.55 mm. The depth D1 of each cut-out portion 200 is: the length from the position corresponding to the rear end of the caulking portion 142 to the bottom of the cutout portion 200.

In the present embodiment, 6 notches 200 are formed in the caulking portion 142. An angle a1 (fig. 5) formed by the center P1 of the virtual circle and each cutout 200 when the gouge part 142 is viewed from the rear side is, for example, 18 ° or more. In this case, the angle occupied by the cutout portion 200 is 108 ° or more over the entire chiseling portion 142(360 °). That is, the ratio of the length of the cut-out portion 200 in the gouging portion 142 to the length of the entire outer periphery of the gouging portion 142 is 0.3 or more. Note that, preferably, the angle a1 formed by the center P1 of the virtual circle and each of the cut-out portions 200 when the gouge portion 142 is viewed from the rear side is 20 ° to 30 °.

Next, the reason why the plurality of notches 200 are formed in the caulking portion 142 will be described. A case where the cut-out portion 200 is not formed at all at the chiseling portion 142 is considered. In this case, when the caulking portion 142 is caulked, the rear end of the caulking portion 142 is pushed inward in the radial direction, and thus the length of the rear end of the caulking portion 142 in the circumferential direction is shortened. As a result, the remaining portion of the bent portion of the caulking portion 142 is caught to the outside in the radial direction, and lateral bulging of the caulking portion, for example, occurs. For example, when the caulking process is performed by pressing the caulking part 142 from the rear end side, the lateral bulge is more conspicuous. For example, depending on the production line, the caulking portion 142 may have to be pressed from the rear end side.

Fig. 6 is a schematic diagram showing a state in which the caulking portion 142 of the case 140 of the gas sensor 100 according to the present embodiment is caulked from the rear. Referring to fig. 6, a cutout portion 200 is formed in a part of the chiseling portion 142 in the circumferential direction. As a result, the total length L1 in the circumferential direction of the portion of the caulking portion 142 where the notch 200 is not formed is shorter than the circumference of the virtual circle C1 surrounded by the rear end of the caulking portion 142 after caulking, for example. Therefore, even if the caulking portion 142 is caulked and the rear end of the caulking portion 142 is pushed inward in the radial direction, the bent portion is easily accommodated inside in the radial direction. As a result, according to the gas sensor 100 of the present embodiment, even if the caulking portion 142 is caulked from the rear, a part of the caulking portion 142 is less likely to catch outside in the radial direction, and therefore, the lateral bulging of the caulking portion 142 is less likely to occur.

[4. characteristics ]

As described above, the cut-out portion 200 is formed in a part of the circumferential direction in the cut-out portion 142 of the gas sensor 100 according to the present embodiment. Therefore, even if the chiseling portion 142 is chiseled and the rear end of the chiseling portion 142 is pushed inward in the radial direction, the bent portion is more easily accommodated inside in the radial direction than in the case where the notch portion 200 is not formed in the chiseling portion 142. As a result, according to the gas sensor 100, even if the chiseling portion 142 is chiseled, a part of the chiseling portion 142 is hard to catch outside in the radial direction, and therefore, the lateral bulging of the chiseling portion 142 is hard to occur.

[5. modification ]

Although the embodiments have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit thereof. Hereinafter, a modified example will be described.

＜5－1＞

In the gas sensor 100 according to the above embodiment, the sensor element 101 is formed with the first internal cavity 20 and the second internal cavity 40. That is, sensor element 101 is a dual cavity structure. However, sensor element 101 need not be a dual cavity structure. For example, the sensor element 101 may be a three-cavity structure.

Fig. 7 is a schematic cross-sectional view schematically showing an example of the structure of the sensor element 101X having a three-cavity structure. As shown in fig. 7, the second internal cavity 40X and the third internal cavity 61 may be formed by further dividing the second internal cavity 40 (fig. 2) into 2 cavities by the fifth diffusion rate control portion 60. In this case, the auxiliary pump electrode 51X may be disposed in the second internal cavity 40X, and the measurement electrode 44X may be disposed in the third internal cavity 61. In the case of the three-chamber structure, the fourth diffusion rate controller 45 may be omitted.

＜5－2＞

In the gas sensor 100 according to the above embodiment, the 6 notches 200 are formed in the caulking portion 142. However, the number of the cutout portions 200 formed in the caulking portion 142 is not limited to 6. For example, the number of the cutout portions 200 formed in the caulking portion 142 may be 1 or more.

Fig. 8 is a diagram corresponding to fig. 5 of a modification. As shown in fig. 8, the housing 140Y has a chiseling portion 142Y. The caulking portion 142Y is provided with 4 cutout portions 200Y. The shape of the densified portion 142 may be such a shape.

[6. examples, etc. ]

< 6-1. examples 1-4 and comparative example 1 >

The same product (one-time assembly) as a part of the gas sensor 100 shown in fig. 1 is manufactured. Examples 1 to 4 and comparative example 1 each differ only in the shape of the chisels.

In example 1, the number of the cutout portions in the gouging portion was 4. The ratio of the length of the cut-out portion in the caulking portion to the length of the entire outer periphery of the caulking portion was 1/3. The depth of the cut portion (D1 in fig. 4) was 2.55 mm. The thickness of the chisel portion was 0.56 mm.

In example 2, the number of the cut portions in the caulking portion was 6. The ratio of the length of the cut-out portion in the caulking portion to the length of the entire outer periphery of the caulking portion was 1/3. The depth of the cut portion was 2.55 mm. The thickness of the densified portion was 0.56 mm.

In example 3, the number of the cut portions in the caulking portion was 4. The ratio of the length of the cut-out portion in the caulking portion to the length of the entire outer periphery of the caulking portion was 1/2. The depth of the cut portion was 2.55 mm. The thickness of the chisel portion was 0.56 mm.

In example 4, the number of the cutout portions in the gouging portion was 6. The ratio of the length of the cut-out portion in the caulking portion to the length of the entire outer periphery of the caulking portion was 1/2. The depth of the cut portion was 2.55 mm. The thickness of the densified portion was 0.56 mm.

In comparative example 1, no notch was formed in the caulked portion. The thickness of the densified portion was 0.56 mm.

The characteristics of examples 1 to 4 and comparative example 1 are summarized in table 1 below.

TABLE 1

< 6-2. test >

(6-2-1. computerized tomography of chiseling section)

Computed Tomography (CT) was performed on each of the primary assemblies of examples 1 to 4 and comparative example 1. Whether the chiseling portion has a lateral bulge is confirmed based on the image generated by the CT.

(6-2-2. leak test)

The leak test was performed using the primary assembly. The air tightness of the holding member and the sensor element was checked by a leak test.

Fig. 9 is a schematic explanatory diagram of a leak test using the tester 500. As shown in fig. 9, the tester 500 includes a mounting fixture 502, an upper housing 504, a lower housing 506, and a tube 508. The mounting jig 502 is formed with a female screw portion (not shown) to which a male screw portion (not shown) of the primary assembly can be attached. The upper cover 504 and the lower cover 506 cover the upper and lower sides of the mounting jig 502. The tube 508 is connected to an opening of the lower housing 506. The connection portions of the upper cover 504, the mounting fixture 502, and the lower cover 506 are sealed by O-rings. The primary assembly in which the seal tape is wound around the male screw portion is attached to the female screw portion of the attachment jig 502 and fixed by a torque wrench (4.0 Nm).

Accordingly, the inside of the upper cover 504 and the inside of the lower cover 506 become: except through the inside of the primary assembly, no gas flows through each other. A soapy water film 510 is attached to the inside of the pipe 508. In this state, air was supplied from the upper opening of the upper cover 504, and a pressure of 0.4MPaG was applied for 1 minute, and the amount of rise (mm) of the film 510 was measured with a ruler. Then, the amount of increase is converted into a leakage amount (cc/min). The 1mm rise corresponds to 0.01cc (═ 0.01 cm) ³ ) The amount of leakage. The smaller the leakage amount, the higher the airtightness of the holding member 143 and the sensor element 101.

< 6-3. test result >

(6-3-1. computerized tomography of chiseling section)

According to the CT result, the following results are obtained: in examples 1 to 4, buckling deformation hardly occurred in the gouged portion, and lateral bulging of the gouged portion hardly occurred. The gouging shape is linear. On the other hand, in comparative example 1, the caulking portion was buckled and deformed, and the caulking portion was laterally bulged. Further, the gouging shape is a curled shape.

Fig. 10 is a diagram showing an example of the calking shape of comparative example 1. As shown in fig. 10, in comparative example 1, the lateral bulge occurred at the caulking portion. Further, a break point appears near the rear end of the caulking portion, and the caulking shape is a curled shape.

Fig. 11 is a diagram showing an example of the calking shape of embodiment 1. As shown in fig. 11, in example 1, no lateral bulge occurred in the caulking portion. In addition, a break point appears near the root of the chiseled portion, and the chiseled shape is linear. In examples 2 to 4, as in example 1, the lateral bulge of the densified portion did not occur.

(6-3-2. leak test)

For examples 1 to 4 and comparative example 1, 3 primary assemblies were prepared and subjected to a leak test. The results of the leak test are shown in table 2 below.

TABLE 2

It can be confirmed that: the leakage amount of each of examples 1 to 4 was smaller than that of comparative example 1.

Claims

1. A gas sensor is provided with:

a sensor element for measuring the concentration of a predetermined gas component in a gas to be measured;

a holding member that holds a part of the sensor element; and

a housing that houses the sensor element and the holding member,

the housing includes:

a cylindrical base; and

a cylindrical caulking portion provided further toward the rear end side than the base portion and pressing a position on the rear end side of the holding member in a bent state,

the chisel-shaped portion is partially formed with a cutout portion in a circumferential direction.

2. The gas sensor according to claim 1,

the ratio of the length of the cut-out portion in the outer periphery of the gouge portion to the length of the entire outer periphery of the gouge portion is 0.3 or more.

3. The gas sensor according to claim 1,

the ratio of the length of the cutout portion in the outer periphery of the gouge portion to the length of the entire outer periphery of the gouge portion is 0.25 to 0.45.

4. The gas sensor according to any one of claims 1 to 3,

the number of the cut portions formed in the chiseling portion is 4 to 6.

5. The gas sensor according to any one of claims 1 to 4,

the length from the position of the chiseling section corresponding to the rear end to the bottom of the cutout section is 2.00mm to 3.00 mm.

6. The gas sensor according to any one of claims 1 to 5,

the thickness of the chiseling portion is 0.45mm to 0.65 mm.